ARS | Publication request: Incomplete transfer of accessory loci influencing SbMATE expression underlies genetic background effects for aluminum tolerance in sorghum

Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 13, 2012
Publication Date: January 4, 2013
Repository URL: http://DOI: 10.1111/tpj.12029
Citation: Melo, J., Lana, U., Pineros, M., Alves, V., Guimaraes, C., Liu, J., Zheng, Y., Zhong, S., Fei, Z., Maron, L., Schaeffert, R., Kochian, L.V., Magalhaes, J. 2013. Incomplete transfer of accessory loci influencing SbMATE expression underlies genetic background effects for aluminum tolerance in sorghum. Plant Journal. 73(2):276-288.

Interpretive Summary: Over 20 percent of the U.S. land area and approximately 50 percent of the world’s arable lands are acidic (pH Technical Abstract: Impaired root development caused by aluminum (Al) toxicity is a major cause for grain yield reduction for crops cultivated on acid soils which are widespread worldwide. In sorghum, the major Al tolerance locus, AltSB, is due to the function of SbMATE, which is an Al-activated root citrate transporter. Here we conducted a molecular and physiological characterization of different AltSB donors and near-isogenic lines (NILs) harboring different AltSB alleles. We observed partial transfer of Al tolerance from the parents to the NILs that was consistent across donor alleles, emphasizing the occurrence of strong genetic background effects related to AltSB. This reduction in tolerance was variable, with a 20% reduction being observed when highly Al tolerant lines were the AltSB donors and as great as 70% when other AltSB alleles were introgressed. This reduction in Al tolerance was closely correlated with a reduction in SbMATE expression in NILs, suggesting incomplete transfer of regulatory loci acting in trans on SbMATE. Nevertheless, AltSB alleles from the highly Al tolerant sources, SC283 and SC566, were found to retain high SbMATE expression presumably via elements present within or near the AltSB locus, resulting in significant transfer of the Al tolerance phenotype to the derived NILs. Allelic effects could not be explained by coding region polymorphisms, although occasional mutations may affect Al tolerance. Finally, we report on the extensive occurrence of alternative splicing for SbMATE, which by means of the non-sense mediated RNA decay pathway, may be an important component regulating SbMATE expression in sorghum.